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30 cell biology > L13 - Cell Cycle > Flashcards

L13 - Cell Cycle Flashcards

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1
Q

purpose of the cell cycle?

A

copy entire genome for :
growth
replacement of lost/damaged cells
maintain cell number

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2
Q

how do prokaryotes divide

A

binary fission

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3
Q

describe process of prokaryote division

A
  1. DNA is attached to membrane
  2. cell enlarges and DNA duplicates
  3. septum forms (___|___) in middle of cell with DNA either side
  4. cells separate
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4
Q

what is unusual about DNA replication and cytokinesis in prokaryotes

A

they occur at same time - so have to be coordinated

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5
Q

describe DNA replication in prokaryotes

A
  1. there is 1 origin of replication
  2. helicase catalyses DNA unwinding forming two replication forks at origin (bidirectional)
  3. DNA pol works around DNA until the bottom where two circular copies are formed
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6
Q

describe prokaryote cytokinesis

A
  1. FtsZ is a protein that forms a ring of protein around the middle of the inner surface of PM
  2. this ring contracts
  3. PM on each side becomes so close that they fuse
  4. two cells
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7
Q

do cytokinesis and DNA replication take the same amount of time? (in prokaryotes)

A

no, DNA replication takes longer

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8
Q

how is DNA rep and cytokinesis co ordinated in prokaryotes

A

cells undergo multifork replication to ensure at least 1 round of replication is completed before cytokinesis

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9
Q

what is multifork replication

A

DNA replication is initiated before previous is completed

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10
Q

what are the phases of the Eukaryotic cell cycle (in order)

A
  1. G1
  2. S
  3. G2
  4. mitosis
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11
Q

describe what happens in G1

A

growth phase

doubling of organelles, proteins, enzymes etc

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12
Q

what happens in S phase

A

DNA replication

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13
Q

why mustn’t the newly replicated sister chromatids be separated too soon? how are they kept together

A

would affect attachment of mitotic spindle

hoop of cohesin around the pair held together by kleisin

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14
Q

what happens in G2

A

preparation for mitosis

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15
Q

what 3 events mark the beginning of mitosis

A
  1. chromosome condensation
  2. nuclear envelope breakdown
  3. mitotic spindle formation
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16
Q

what is interphase

A

G1 S G2

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17
Q

what happens during prophase

A
  1. chromosome condensation - condensin circles DNA and compresses (C become visible)
  2. nuclear envelope breaks down
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18
Q

why must the nuclear envelope break down early on in mitosis

A

so the spindle has access to the chromosomes

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19
Q

what happens during metaphase

A

mitotic spindle formation

chromosomes line up on equator

20
Q

what happens during anaphase

A

separation of sister chromatids - kleisin cleaved, cohesin ring opens up, spindle attaches and begins shortening

21
Q

what happens during telophase

A

chromatids separated to either end of cell

22
Q

describe the process of cytokinesis

A
  1. nuclear membrane begins to reform
  2. cytoplasm divided in two by contractile ring of actin &myosin 2 filaments
  3. membranes pinch from outside in into two cells in middle
23
Q

cell cycle variations : explain how cell cycles vary time wise

A
  1. timing differs between species

2. timing differs due to part of body cell is from eg liver 1 year cycle

24
Q

cell cycle variations : how do cell cycles differ in size

A

eg somatic cells all same size as they grow after division

embryonic cells divide without growing so cells get smaller with each division

25
Q

cell cycle variations : how do cell cycles differ in nuclear envelope dynamics

A

multicellular - open mitosis - nuclear envelope breaks down because spindle is outside nucleus
unicellular - closed mitosis - NE doesn’t break down

26
Q

what is anchorage dependence

A

cells must be attatched to a surface to be able to divide

27
Q

what is density dependant inhibition

A

cells stop dividing when they contact eachother (eg fill up a flat surface)

28
Q

how is cell cycle controlled

A
  1. cell cycle engine
  2. co ordination (replicated DNA must undergo mitosis before replicating again)
  3. checkpoints

also
anchorage dependence
density dependant inhibition

29
Q

explain the position of Restriction point checkpoint and its function

A

end of G1 before S

decides whether to initiate new cycle

30
Q

explain the position and function of G2 checkpoint

A

in G2, checks if S phase has been completed

31
Q

explain the location and function of the spindle checkpoint

A

start of mitosis

ensures spindle is attached to each chromosome

32
Q

explain location of DNA damage checkpoint and its function

A

throughout cell cycle

if damage detected, cycle paused and fixed

33
Q

what can failure in the DNA damage checkpoint lead to

A

damaged DNA being replicated - mutation - cancer

34
Q

what can failure in the Restriction point checkpoint lead to

A

uncontrolled initiation of cell cycles - tumours

35
Q

what can failure in the spindle checkpoint lead to

A

failure to separate chromosomes equally - aneuploidy/downsyndrome

36
Q

accumulation of what protein will trigger cytokinesis in prokaryotes

A

FtsZ

37
Q

what proteins ensure sister chromatids aren’t separated to early during mitosis and how

A

cohesin forms a loop held shut by kleisin

38
Q

what protein mediates the centromere

A

kinetochore

39
Q

what drives the cell cycle

A

cyclin and cyclin dependant kinase (CDK)

40
Q

what 3 things will halt cell cycle

A
  1. no nutrients
  2. damaged DNA
  3. chromosomes fail to attach to mitotic spindle
41
Q

what is the cell cycle engine

A

the protein complex that drives the cell cycle

42
Q

what happens to levels of CDK throughout the cell cycle

A

remains the same, its the activity that changes

43
Q

what happens to levels of cyclins throughout the cell cycle

A

rise and fall

44
Q

what phase does cyclin E drive and what is the name of the cyclin involved

A

G1 into S

G1/S CDK

45
Q

what phase of the cycle does cyclin B drive and what is the name of the cyclin involved

A

G2 into mitosis (induces NE breakdown)

M CDK

30 cell biology (21 decks)

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